What Causes Pelvic Pain Post Menopause?

I am 66 years old, post menses and I have been experiencing pelvic pain for about a month now. I am 5'4", 250 lbs. No weight change, but my body shape is changing and I'm experiencing constant bloated feeling. My only diagnosed problem is osteoarthritis and I had a hip replacement about 6 years ago (not from arthritis, a staph infection). I'm exhausted constantly.